Technical advances in high-performance wind turbine generators (WTGs) are driving increasingly demanding requirements for their power converters, particularly in Type 4 WTGs, where the full generator power is fed into the grid via power converters. From a power electronics perspective, WTGs represent a high-power, low-voltage application, resulting in relatively high current requirements. Due to the limited current-carrying capability of individual power semiconductors, the desired output power is typically achieved by using multiple parallel power converters. While such architectures improve scalability, they also introduce internal interactions between the parallel power converters in the form of circulating currents, which are not explicitly addressed by conventional current control schemes.

This paper proposes a coordinated current control (CCC) approach for WTGs with multiple parallel power converters, focusing on the grid-side converters. By applying a decoupling transformation, the method separates the current fed into the grid from internal circulating currents, enabling independent control of system output and converter interactions. In contrast to conventional approaches with individual current controllers per converter, the CCC exploits the additional degrees of freedom of multi-converter systems to improve overall performance, particularly with respect to power quality (e.g., harmonic content of the grid current) and fault-ride-through behavior (e.g., response to fast transients).

The theoretical framework is derived based on analytical models of parallel polyphase systems. Using this framework, the proposed control scheme is evaluated in a Model-in-the-Loop simulation of a WTG with four parallel converters and compared to a state-of-the-art reference controller. The evaluation comprises a series of simulation scenarios, including varying grid conditions (e.g., weak and strong grids), various grid fault cases, and multiple controller parameterizations, including different configurations of resonance controllers for harmonic compensation. The simulation results demonstrate improved dynamic performance during grid faults and enhanced power quality while preventing unwanted interactions between parallel power converters.The approach is further validated using Hardware-in-the-Loop simulations and experimental investigations on a full-scale WTG (results pending).